The contents of Japanese Patent Application No. 11-356622, with a filing date of Dec. 15, 1999, in Japan, is incorporated by reference herein, in its entirety.
The present invention relates generally to an evaporative emission control apparatus for a motor vehicle, and more particularly to a supporting structure of a canister within a fuel tank.
A conventional evaporative emission control apparatus is provided with a canister that contains an adsorbent material made of activated charcoal, which is able to adsorb evaporative fuel. The canister adsorbs the evaporative fuel generated in the fuel tank. Then the canister is purged and supplies the evaporative fuel to an intake system of an internal combustion engine when it is in operation. In this way, the evaporative emission control apparatus reduces the evaporative fuel released into the atmosphere.
In the structure described above, since the canister is a component of a fuel supplying system of a motor vehicle, it is generally disposed in an engine compartment or under a floor panel of the vehicle body.
Recently, it has been recognized that the adsorbability of the adsorbent material depends on its temperature. Japanese Provisional Patent (Kokai) Publication No. 64-347 (1989) discloses a canister disposed in the fuel tank in order to improve the adsorbability of the adsorbent material by preventing the temperature thereof from changing as much as possible.
Specifically, it discloses the fuel tank having an opening on the upper shell thereof, and the canister inserted through the opening into the fuel tank. The top surface of the canister closes the opening as a lid.
The periphery of the top surface of the canister is fixed to the periphery of the opening by means of, for example, bolts and nuts, and sealing material, such as packing made of a synthetic resin, is provided between these peripheries.
In the prior art described above, although the canister is disposed in the fuel tank, the top surface of the canister closes the opening of the fuel tank as a lid, and, therefore, makes itself a part of the upper shell of the fuel tank. That is, it can be said that top surface of the canister is brought into direct and broad contact with the upper shell of the fuel tank.
If a surface of the canister is in direct and broad contact with a shell of the fuel tank, the canister can be easily affected by the environment temperature outside the fuel tank, which depends on an air temperature, heat radiation from an exhaust tube disposed near the fuel tank, and heated air from the engine compartment. The change of the environment temperature may cause the adsorption of the adsorbent material disposed in the canister to be unstable.
And recently, other than the sealing material such as packing, some other components of the fuel supplying system, such as a casing of the canister, evaporative fuel passages connected thereto, for example, are made of a synthetic resin. Therefore, the evaporative fuel (mostly comprising HC or hydrocarbon) may penetrate through the synthetic resin material of which packing or other components are made, although it may be a very small quantity.
Therefore when the top surface of the canister is used as a lid that closes the opening of the fuel tank as the prior art discloses, a small amount of the evaporative fuel may be released into the atmosphere by penetrating through the packing or other components made of a synthetic resin.
Since the need for reducing the evaporative fuel released into the atmosphere for improving the environmental protection is getting more important, there is a need to reduce the evaporative fuel released into the atmosphere as much as possible.
Therefore, a general object of the invention is to provide an improved evaporative emission control apparatus that alleviates one or more of the shortcomings discussed earlier herein.
An object of the invention is to provide an evaporative emission control apparatus that can provide stable adsorption of the evaporative fuel.
Another object of the invention is to provide an evaporative emission control apparatus that reduces the evaporative fuel released into the atmosphere, by penetrating through a synthetic resin material, as much as possible.
The above and other objects of the present invention can be accomplished by an evaporative emission control apparatus for a motor vehicle that includes a fuel tank having a tank shell to store fuel therein, a canister disposed within the fuel tank to adsorb and temporarily store evaporative fuel generated in the fuel tank, and a bracket that is secured to the fuel tank to support the canister apart from the tank shell.
According to one aspect of the present invention, the canister is disposed in the fuel tank by the bracket, and the outer surface of the canister is arranged apart from the inner surface of the tank shell. Therefore the canister is less influenced by the environment temperature around the fuel tank, and the adsorption of the evaporative fuel can be kept stable.
Furthermore, even if the outer surface of the canister is made of a synthetic resin, penetration of the evaporative fuel through the outer surface causes few problems because the entire canister is disposed within the fuel tank, and arranged apart from the inner side of the tank shell. Furthermore, the evaporative fuel cannot penetrate outside of the fuel tank between the peripheries of the opening on the tank shell and the top surface of the canister, as is the case in the prior art structures. Therefore the present invention reduces the evaporative fuel released into the atmosphere.
The evaporative emission control apparatus described above may further include a first connector that connects an evaporative fuel passage with the canister, and a supporting point where the canister is supported to the bracket. may be located proximate to the first connector.
According to the structure mentioned above, since the bracket reduces the movements of the canister around the supporting point, the bracket also reduces the moment around the first connector as much as possible. Therefore, the first connector maintains a firm connection to the evaporative fuel passage.
The evaporative emission control apparatus described above may further include a second connector that penetrates through the tank shell, and a securing point where the bracket is secured to the fuel tank may be located proximate to the second connector.
According to the structure mentioned above, the evaporative fuel passage connected to the canister and to the second connector can be made as short as possible, and occupies as little as possible of the inner space of the fuel tank. Therefore it makes it easier to arrange the evaporative fuel passage and other components in the fuel tank.
Furthermore, even if the evaporative fuel passage is made of a synthetic resin, a shorter passage makes its area through which the evaporative fuel can penetrate smaller, so that the evaporative fuel that penetrates through the evaporative fuel passage can be reduced, and the evaporative fuel released into the atmosphere can be reduced as much as possible.
When the canister is disposed within the fuel tank apart from the tank shell, the canister may be hung on an upper portion of the fuel tank by the bracket.
According to the structure mentioned above, since the second connector is generally located on the upper part of the fuel tank, the evaporative fuel passage connected to the canister and to the second connector can be made much shorter, and occupies less of the inner space of the fuel tank. Therefore it becomes much easier to arrange the evaporative fuel passage and other components in the fuel tank.
Furthermore, the bracket may be elastically deformable.
According to the structure mentioned above, a resilient portion is formed on the bracket, and it can absorb the load brought to the canister caused by vibrations of the vehicle and/or the inertial force of the canister at a time of acceleration or deceleration of the vehicle, so that the resilient portion can prevent the concentration of the load brought to the securing point, and the fuel tank can be protected effectively.
The bracket may also have an yielding portion between the securing point and the supporting point.
According to the structure mentioned above, the yielding portion can absorb the excessive load caused by a collision of the vehicle by a deformation and/or a rupture thereof. In the manner described above, the yielding portion can prevent the concentration of the load brought to the securing point, and the fuel tank can be protected more effectively.
The evaporative emission control apparatus of the present invention may further include a guide bracket disposed in the fuel tank to support a lower part of the canister and prevent horizontal movements thereof.
According to the structure mentioned above, the guide bracket supports the lower part of the canister against the load caused by vibrations of the vehicle and/or the inertial force of the canister at a time of acceleration or deceleration of the vehicle so that it can prevent horizontal movements of the canister, and thereby provide stable support.
The evaporative emission control apparatus of the present invention may further include a resilient support member to support the lower part of said canister and reduce vertical movements thereof.
According to the structure mentioned above, the resilient support member can reduce vertical movements of the canister caused by vibrations of the vehicle, so that it can lighten the load brought to the bracket to support the canister.
Further objects, features and advantages of the present invention will become apparent from the Detailed Description of Preferred Embodiments which follows when read in light of the accompanying figures and the claims.